Liquid crystal displays are commonly used as display devices for compact electronic apparatuses, because they not only provide good quality images but are also very thin. Because liquid crystal in a liquid crystal display does not emit any light itself, the liquid crystal has to be lit by a light source so as to clearly and sharply display text and images. Therefore, liquid crystal displays typically require a backlight module.
Referring to FIG. 11, a typical backlight module 80 includes a frame-shaped piece of double-sided adhesive masking tape 81, a first brightness enhancement film (BEF) 82, a second BEF 83, a diffusing film 84, a light guide plate 85, and a plastic frame 86, arranged generally in that order from top to bottom. The backlight module 80 further includes a plurality of light emitting diodes (LEDs) 87 disposed adjacent to a light incident surface 852 of the light guide plate 85.
The light guide plate 85 further includes a light emitting surface 854 perpendicularly connected with the light incident surface 852, and two opposite side surfaces 856 perpendicularly connected with both the light incident surface 852 and the light emitting surface 854. A pair of ears 858 outwardly extends from the each of side surfaces 856. Top surfaces (not labeled) of the ears 858 are coplanar with the light emitting surface 854. The first BEF 82, the second BEF 83, and the diffusing film 84 are generally rectangular, and have a same size corresponding to a size of the light emitting surface 854. The plastic frame 86 includes a frame-shaped supporting board 860. A pair of notches 862 is defined in an inner wall of each of two opposite long sides of the supporting board 860.
The light guide plate 85 is generally made to be very thin in order that the backlight module 80 can be compact. On the other hand, the plastic frame 86 needs to have a minimum thickness in order to provide the backlight module 80 with sufficient mechanical strength. Thus when the backlight module 80 is assembled, the light guide plate 85 is received in the plastic frame 86. The ears 858 of the light guide plate 85 are respectively received in the notches 862 of the supporting board 860. In general, a gap exists between the top surface of each of the ears 858 and a top surface of the supporting board 860. The masking tape 81 is then adhered to top edge portions of the supporting board 860 and adjacent peripheral edge portions of the first BEF 82. Thus the gap is defined between the top surface of each of the ears 858 and the masking tape 81. That is, portions of the masking tape 81 over the notches 862 of the supporting board 860 are not utilized in providing adhesion between the supporting board 860 and the first BEF 82. This means the mechanical stability of the backlight module 80 may be compromised.
What is needed, therefore, is a backlight module that can overcome the above-described deficiencies. What is also needed is a liquid crystal display including the backlight module.